Overset simulation of a submarine and propeller in towed, self-propelled and maneuvering conditions

Abstract

Simulations of the free running submarine model DARPA Suboff in a horizontal overshoot maneuver are presented. To perform the simulations, the fully appended hull was fitted with the conceptual submarine propeller E1619. The overset flow solver CFDShip-Iowa v4.5 was used to perform the computations, including coupling with the propeller code PUF-14. Propeller open water curves were obtained for two grids over a wide range of advance coefficients covering high to moderately low loads, with results compared to available experimental data. The open water curves were also simulated with the coupled CFDShip-Iowa/PUF-14 approach. While computations are performed with delayed detached-eddy simulation (DDES), simulations with Reynolds-averaged Navier–Stokes (RANS), detached-eddy simulation (DES) and with no turbulence model were also performed. Results show that RANS overly dissipates the wake while the solution with no turbulence model shows unphysical instability in the tip vortices. Overall, open water curves are predicted well by the discretized propeller and by the coupled CFDShip-Iowa/PUF-14 approach. The towed DARPA Suboff hull fitted with sail, rudders and stern planes was simulated and results were compared against experimental data, showing satisfactory results. Self-propulsion computations of the DARPA Suboff fitted with the E1619 propeller were performed and the resulting propeller performance analyzed, both using a rotating gridded propeller and the CFDShip-Iowa/PUF-14 approach. A 20/10 overshoot maneuver is demonstrated with both approaches, showing that the results are similar when the propeller remains close to straight-ahead conditions, but trends between approaches tend to diverge for large wake distortions and low advance ratios. A more complex simulation of a surfacing maneuver of the submarine in waves is demonstrated showing the potential of the approach to tackle simulations including massive free surface deformations in a realistic environment.